Rohit Seth wrote:> On Fri, 2006-09-15 at 13:26 +0400, Kirill Korotaev wrote:> > <...skipped...>> >> for VMware which can reserve required amount of RAM for VM.>> >> It is much easier to provide guarantees in complete virtual> environments. But then you pay the cost in terms of performance.> "Complete virtual environments" vs. "contaners" is not [only] aboutperformance! In the end, given a proper set of dirty and no-so-dirtyhacks in software and hardware, their performance will be close to native.

Containers vs. other virtualization types is more about utilization,density, scalability, portability.

Speaking of guarantees, yes, guarantees is easy, you just reserve suchamount of RAM for your VM and that is all. But the fact is usually somepart of that RAM will not be utilized by this particular VM. But sinceit is reserved, it can not be utilized by other VMs -- and we end upjust wasting some resources. Containers, given a proper resourcemanagement and configuration, can have some guarantees and still be ableto utilize all the RAM available in the system. This difference can bemetaphorically expressed as a house divided into rooms. Dividing wallscan either be hard or flexible. With flexible walls, room (container)owner have a guarantee of minimal space in your room, but if a fewguests come for a moment, the walls can move to make more space (up tothe limit). So the flexibility is measured as the delta between aguarantee and a limit.

This flexibility leads to higher utilization, and this flexibility isone of the reasons for better density (a few times higher than that of aparavirtualization solution).

I will not touch scalability and portability topics here to make thingssimpler.> I think we should punt on hard guarantees and fractions for the first> draft. Keep the implementation simple.> Do I understand it right that with hard guarantees we loose theflexibility I have just described? If this is the case, I do not like it.-To unsubscribe from this list: send the line "unsubscribe linux-kernel" inthe body of a message to majordomo@vger.kernel.orgMore majordomo info at http://vger.kernel.org/majordomo-info.htmlPlease read the FAQ at http://www.tux.org/lkml/